The present invention is directed to colorant compositions. More specifically, the present invention is directed to colorants particularly useful for imaging applications, such as ink jet inks and the like. One embodiment of the present invention is directed to an aqueous ink composition for ink jet printing which comprises water, a humectant, and a colorant selected from the group consisting of: (a) those of Formula I ##STR3## wherein R.sub.1 is an electron withdrawing group, R.sub.2 is selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, and substituted arylalkyl, R.sub.3 is selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, and substituted arylalkyl, and Ar is selected from the group consisting of aryl, substituted aryl, arylalkyl, and substituted arylalkyl; (b) those of Formula II ##STR4## wherein R.sub.1 is selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, and substituted arylalkyl, R.sub.2 is selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, and substituted arylalkyl, and Ar is selected from the group consisting of aryl, substituted aryl, arylalkyl, and substituted arylalkyl; (c) dimeric compounds containing two moieties of Formula I; (d) dimeric compounds containing two moieties of Formula II; (e) dimeric compounds containing one moiety of Formula I and one moiety of Formula II; (f) trimeric compounds containing three moieties of Formula I; (g) trimeric compounds containing three moieties of Formula II; (h) trimeric compounds containing two moieties of Formula I and one moiety of Formula II; (i) trimeric compounds containing one moiety of Formula I and two moieties of Formula II; (j) polymeric compounds containing at least four moieties selected from the group consisting of Formula I, Formula II, and mixtures thereof; and (k) mixtures thereof.
Another embodiment of the present invention is directed to colorant compositions selected from the group consisting of: (a) dimeric compounds containing two moieties of Formula I ##STR5## wherein R.sub.1 is an electron withdrawing group, R.sub.2 is selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, and substituted arylalkyl, R.sub.3 is selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, and substituted arylalkyl, and Ar is selected from the group consisting of aryl, substituted aryl, arylalkyl, and substituted arylalkyl; (b) dimeric compounds containing two moieties of Formula II ##STR6## wherein R.sub.1 is selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, and substituted arylalkyl, R.sub.2 is selected from the group consisting of hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, arylalkyl, and substituted arylalkyl, and Ar is selected from the group consisting of aryl, substituted aryl, arylalkyl, and substituted arylalkyl; (c) dimeric compounds containing one moiety of Formula I and one moiety of Formula II; (d) trimeric compounds containing three moieties of Formula I; (e) trimeric compounds containing three moieties of Formula II; (f) trimeric compounds containing two moieties of Formula I and one moiety of Formula II; (g) trimeric compounds containing one moiety of Formula I and two moieties of Formula II; and (h) polymeric compounds containing at least four moieties selected from the group consisting of Formula I, Formula II, and mixtures thereof.
Ink jet printing systems generally are of two types: continuous stream and drop-on-demand. In continuous stream ink jet systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The stream is perturbed, causing it to break up into droplets at a fixed distance from the orifice. At the break-up point, the droplets are charged in accordance with digital data signals and passed through an electrostatic field which adjusts the trajectory of each droplet in order to direct it to a gutter for recirculation or a specific location on a recording medium. In drop-on-demand systems, a droplet is expelled from an orifice directly to a position on a recording medium in accordance with digital data signals. A droplet is not formed or expelled unless it is to be placed on the recording medium.
Since drop-on-demand systems require no ink recovery, charging, or deflection, the system is much simpler than the continuous stream type. There are two types of drop-on-demand ink jet systems. One type of drop-on-demand system has as its major components an ink filled channel or passageway having a nozzle on one end and a piezoelectric transducer near the other end to produce pressure pulses. The relatively large size of the transducer prevents close spacing of the nozzles, and physical limitations of the transducer result in low ink drop velocity. Low drop velocity seriously diminishes tolerances for drop velocity variation and directionality, thus impacting the system's ability to produce high quality copies. Drop-on-demand systems which use piezoelectric devices to expel the droplets also suffer the disadvantage of a slow printing speed.
The other type of drop-on-demand system is known as thermal ink jet, or bubble jet, and produces high velocity droplets and allows very close spacing of nozzles. The major components of this type of drop-on-demand system are an ink filled channel having a nozzle on one end and a heat generating resistor near the nozzle. Printing signals representing digital information originate an electric current pulse in a resistive layer within each ink passageway near the orifice or nozzle, causing the ink in the immediate vicinity to evaporate almost instantaneously and create a bubble. The ink at the orifice is forced out as a propelled droplet as the bubble expands. When the hydrodynamic motion of the ink stops, the process is ready to start all over again. With the introduction of a droplet ejection system based upon thermally generated bubbles, commonly referred to as the "bubble jet" system, the drop-on-demand ink jet printers provide simpler, lower cost devices than their continuous stream counterparts, and yet have substantially the same high speed printing capability.
The operating sequence of the bubble jet system begins with a current pulse through the resistive layer in the ink filled channel, the resistive layer being in close proximity to the orifice or nozzle for that channel. Heat is transferred from the resistor to the ink. The ink becomes superheated far above its normal boiling point, and for water based ink, finally reaches the critical temperature for bubble formation or nucleation of around 280.degree. C. Once nucleated, the bubble or water vapor thermally isolates the ink from the heater and no further heat can be applied to the ink. This bubble expands until all the heat stored in the ink in excess of the normal boiling point diffuses away or is used to convert liquid to vapor, which removes heat due to heat of vaporization. The expansion of the bubble forces a droplet of ink out of the nozzle, and once the excess heat is removed, the bubble collapses on the resistor. At this point, the resistor is no longer being heated because the current pulse has passed and, concurrently with the bubble collapse, the droplet is propelled at a high rate of speed in a direction towards a recording medium. The resistive layer encounters a severe cavitational force by the collapse of the bubble, which tends to erode it. Subsequently, the ink channel refills by capillary action This entire bubble formation and collapse sequence occurs in about 10 microseconds. The channel can be retired after 100 to 500 microseconds minimum dwell time to enable the channel to be refilled and to enable the dynamic refilling factors to become somewhat dampened. Thermal ink jet processes are well known and are described in, for example, U.S. Pat. Nos. 4,601,777, 4,251,824, 4,410,899, 4,412,224, and 4,532,530, the disclosures of each of which are totally incorporated herein by reference.
U.S. Pat. No. 4,284,782 (Schmidt), the disclosure of which is totally incorporated herein by reference, discloses a process for the manufacture of 6-hydroxypyrid-2-ones by reacting a cyanoacetamide with an acetoacetic acid ester at temperatures of 50.degree. C. to 200.degree. C. and a pressure of 0.5 to 50 bars in an aqueous solution or suspension in the presence of an amine in a molar amount at least equal to that of the cyanoacetamide reactant. The 6-hydroxypyrid-2-ones are of the general formula ##STR7## wherein R represents hydrogen or an optionally branched alkyl radical having 1 to 4 carbon atoms.
Japanese Patent Publication 04-180968-A discloses a dye represented by the general formula ##STR8## wherein R.sub.1 and R.sub.2 are hydrogen or optionally substituted alkyl and wherein R.sub.1 and R.sub.2 can be formed into a ring of 5 or 6 atoms by bonding with each other, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are halogen, optionally substituted alkyl, optionally substituted alkoxy, optionally substituted amido, or optionally substituted sulphonamide, A, B, and D are either the same or different and are carbon, nitrogen, oxygen, on an organic group or a hydrogen-atom bonding with the pyridone-ring through the sulphur atom. The dye is used for forming color images, such as a cyan colored filter dye used as an image forming medium for a photograph, heat-sensitive transfer printing, ink jet printing, or the like.
While known compositions and processes are useful for their intended purposes, a need remains for improved colorant compositions particularly suitable for use in ink jet printing inks. In addition, there is a need for ink jet inks with improved waterfastness. There is also a need for ink jet inks with improved lightfastness. Further, there is a need for ink jet inks in which lower concentrations of colorant are needed to obtain images of the desired color and intensity. Additionally, there is a need for ink jet inks which generate images of high color quality. There is also a need for ink jet inks with improved latency. A need also remains for for ink jet inks containing dye colorants in which the dye exhibits little or no precipitation from the ink. A need also exists for dyes suitable for use in dye diffusion transfer systems.